Many years ago, in the heyday of domain speculation (after the dot-com crash), some of the largest domain speculators became registrars to gain advantages such as the one you mention.
This conflict of interest was not limited to registrars. Registries got into the game as well, reserving names for the sole purpose of exploiting speculators or speculating themselves.
What the OP could have done instead of taking a random sample is to examine certain nameservers in the com zone. That is, look at certain registrars. This reveals the true extent of parking.
Not sure about the situation today, but in the past many domain registrants were unaware that their registrar was deriving revenue from their "unused" domains The registrants were paying the fees to keep the registrations active and the regsistrar was collecting the ad revenue by setting up parking on the domains.
This conflict of interest was not limited to registrars. Registries got into the game as well, reserving names for the sole purpose of exploiting speculators or speculating themselves.
What the OP could have done instead of taking a random sample is to examine certain nameservers in the com zone. That is, look at certain registrars. This reveals the true extent of parking.
Not sure about the situation today, but in the past many domain registrants were unaware that their registrar was deriving revenue from their "unused" domains The registrants were paying the fees to keep the registrations active and the regsistrar was collecting the ad revenue by setting up parking on the domains.